I have an entire SageMath Jupyter Notebook devoted to Squiganometry. That is some fun stuff to play with!

That is such a clever way to play with asymmetry on several different levels

I have several calculators and electronic organizers that are old enough to drink in the US. A few slide rules that are old enough to retire. I might have some weird stuff in the back of the freezer that would qualify, too.

SageMath is my go to for heavy math.

Nothing will ever hook me as badly as Kerbal Space Program did. If I wasn't at work, I was playing Kerbal for five years straight. No breaks, didn't play anything else during that time. Once I got RealSolarSystem and RealismOverhaul working, you couldn't pry me away from the computer. I put in aver 10,000 hours, easily.

Happy to help!

It's a lovely pen, and I just bought one myself! The trick to getting a full-ish fill is to dunk the nib in the ink and rapidly push on the button about eight or nine times. You'll feel a difference in the button action when it gets as full as it is going to. The button will give a bit of resistance at that point. I don't remember if mine got completely full, but I know that it holds a decent amount of ink. I hope that helps!

You can't increase the font size, but it is larger than the HP Prime and TI nspire CXII on large font.

I just dug through the offerings of all of the niche calculator manufacturers I can think of and came up empty handed. What I would recommend in your case is the Casio fx-CG50, though. It has rubber pads on the back of the case and enough heft that it doesn't move when placed on a desk and used one-handed. The screen is easily visible from most angles and it has the largest font of all of my graphing calculators.